Fluid infusion system, a method of assembling such system and drug reservoir for use in the system

Abstract

The present invention relates to methods and devices for providing a reduced risk of free flow from medical devices such as an infusion pump. A medicament containing reservoir is provided with a piston having a sealing portion formed by a material of a first stiffness. The piston further comprises a frictional enhancing member having one or more reservoir wall engaging portions and being at least partly made of a material having a stiffness greater than the first stiffness. By arranging the frictional enhancing member to exert a radially outwards directed force component against the cylindrical wall an increased friction is provided between the piston and the reservoir wall.

The invention claimed is: 
     
       1. A fluid infusion system for infusing a medication fluid comprising:
 a reservoir adapted to contain the fluid and adapted for use with a pump drive system having a linear actuation member, the reservoir comprising: 
 a proximal end adapted to connect to an infusion set; 
 an open distal end; 
 a cylindrical reservoir wall that extends along a longitudinal axis from the proximal end to the distal end; and 
 a piston adapted to be slideably and frictionally mounted within the reservoir and forming a fluid-tight bather inside the reservoir; the piston comprising a piston body with at least one peripheral sealing portion made of a material having a first stiffness, said at least one sealing portion in sealing contact with the inside surface of the reservoir wall, 
 
       wherein the piston further comprises a friction enhancing member adapted to be coupled to the piston, the friction enhancing member comprising a central section and one or more wall engaging portions coupled to the central section by a respective flexible shank portion bridging the one or more wall engaging portions with the central section, wherein the one or more wall engaging portions are at least partially made of a material having a greater stiffness than said first stiffness, the one or more wall engaging portions frictionally engaging the cylindrical wall of the reservoir and being arranged to exert a radially outwards directed force component against the cylindrical wall, and wherein the respective flexible shank portion(s) is/are so configured that the respective wall engaging portions(s) is/are movable relative to the central section only in directions substantially perpendicular to said longitudinal axis. 
     
     
       2. The fluid infusion system as defined in  claim 1 , wherein at least a part of each of the respective flexible shank portions are formed as longitudinally extending members forming an angle greater than 20 degrees relative to a plane perpendicular to said longitudinal axis. 
     
     
       3. The fluid infusion system as defined in  claim 1 , wherein at least one of the one or more wall engaging portions extends in a plane generally perpendicular to the longitudinal axis of the reservoir. 
     
     
       4. The fluid infusion system as defined in  claim 1 , wherein at least one of the one or more wall engaging portions extends at an inclined angle with respect to a plane arranged perpendicular to the longitudinal axis of the reservoir. 
     
     
       5. The fluid infusion system as defined in  claim 1 , wherein at least one of the one or more wall engaging portions is provided with an arcuate surface shaped to abut the interior wall surface of the cylindrical reservoir wall along the arcuate surface. 
     
     
       6. The fluid infusion system as defined in  claim 1 , wherein the piston body has a first external proximate side being adapted to contact the fluid and an external distal side defining an opening leading into a cavity, and said frictional enhancing member is fixedly retained inside said cavity. 
     
     
       7. The fluid infusion system as defined in  claim 6 , wherein said piston further comprises a third member adapted to releasably couple to said linear actuation member and adapted to fixedly secure said third member to at least one of said friction enhancing member and said piston body. 
     
     
       8. The fluid infusion system as defined in  claim 7 , wherein said linear actuation member comprises one or more protrusions and the third member is adapted to engage said one or more protrusions. 
     
     
       9. The fluid infusion system as defined in  claim 1 , wherein said friction enhancing member is at least partly made of steel or spring steel. 
     
     
       10. The fluid infusion system as defined in  claim 1 , wherein the piston body and the at least one sealing portion are formed unitarily. 
     
     
       11. The fluid infusion system as defined in  claim 1 , wherein the piston body is made of a material having a greater stiffness than the material of the at least one sealing portion, and the piston body and the friction enhancing member are formed unitarily. 
     
     
       12. The fluid infusion system as defined in  claim 1 , wherein the piston is formed by co-molding said piston body and said friction enhancing member so that said friction enhancing member is partly encapsulated by the piston body. 
     
     
       13. A method for assembling a fluid infusion system suitable for infusing a medication fluid, the method comprising:
 providing a fluid infusion pump comprising a drive system having a linear actuation member; 
 providing a reservoir adapted to contain the fluid, the reservoir comprising:
 a proximal end adapted to connect to an infusion set; 
 an open distal end; 
 a cylindrical reservoir wall that extends along a longitudinal axis from the proximal end to the distal end; and 
 a piston adapted to be slideably and frictionally mounted within the reservoir and forming a fluid-tight bather inside the reservoir; the piston comprising a piston body with at least one peripheral sealing portion made of a material having a first stiffness, said at least one sealing portion in sealing contact with the inside surface of the reservoir wall, wherein the piston further comprises a friction enhancing member adapted to be coupled to the piston, the friction enhancing member comprising a central section and one or more wall engaging portions coupled to the central section by a respective flexible shank portion bridging the one or more wall engaging portion with the central section, wherein the wall engaging portion(s) is/are at least partially made of a material having a greater stiffness than said first stiffness, at least one wall engaging portion frictionally engaging the cylindrical wall of the reservoir and being arranged to exert a radially outwards directed force component against the cylindrical wall and wherein the respective shank portion(s) is/are so configured that the respective wall engaging portion(s) is/are movable relative to the central section only in directions substantially perpendicular to said longitudinal axis; and 
 
 coupling the reservoir to the infusion pump. 
 
     
     
       14. A reservoir for use in the fluid infusion system according to  claim 1 , the reservoir adapted to contain a fluid for infusion into the body of a patient and adapted for use with a drive system having a linear actuation member, the reservoir comprising:
 a proximal end adapted to connect to an infusion set; 
 an open distal end; 
 a cylindrical reservoir wall that extends along a longitudinal axis from the proximal end to the distal end; and 
 a piston adapted to be slideably and frictionally mounted within the reservoir and forming a fluid-tight bather inside the reservoir; the piston comprising a piston body with at least one peripheral sealing portion made of a material having a first stiffness, said at least one sealing portion in sealing contact with the inside surface of the reservoir wall, 
 wherein the piston further comprises a friction enhancing member comprising a central section and one or more wall engaging portions coupled to the central section by a respective flexible shank portion bridging the one or more wall engaging portion with the central section, wherein the one or more wall engaging portions are at least partially made of a material having a greater stiffness than said first stiffness, the one or more wall engaging portions frictionally engaging the cylindrical wall of the reservoir and being arranged to exert a radially outwards directed force component against the cylindrical wall, and wherein at least one of the respective flexible shank portion(s) is/are so configured that the respective wall engaging portion(s) is/are movable relative to the central section only in directions substantially perpendicular to said longitudinal axis. 
 
     
     
       15. A fluid infusion system for infusing a medication fluid, the fluid infusion system comprising:
 a fluid reservoir having a cylindrical wall that extends along a longitudinal axis defining an inside and outside surface; 
 a piston adapted to be slideably and frictionally mounted within the reservoir and forming a fluid-tight bather inside the reservoir; the piston comprising a piston body with at least one sealing portion made of a material having a first stiffness, the sealing portion being in sealing contact with the inside surface of the fluid reservoir; 
 a friction enhancing member that is independent of the sealing portion and is configured to mate with the sealing portion, and comprises at least one wall engaging portion coupled to the central section by a respective flexible shank portion bridging the one or more wall engaging portions with the central section, that is at least partially made of a material having a greater stiffness than the first stiffness of the sealing portion, wherein the at least one wall engaging portion frictionally engages the inside surface of the fluid reservoir and exerts a force component in a radially outward direction against the inside surface of the fluid reservoir; and 
 a linear actuation member operatively associated with the friction enhancing member, and wherein at least one of the respective flexible shank portion(s) is/are so configured that the respective wall engaging portion(s) is/are movable relative to the central section only in directions substantially perpendicular to said longitudinal axis. 
 
     
     
       16. A reservoir as defined in  claim 14 , wherein at least a part of each of the respective flexible shank portions are formed as longitudinally extending members forming an angle greater than 20 degrees relative to a plane perpendicular to the longitudinal axis.